Field of the Invention
The invention relates to the field of energy materials, and, in particular, to a modified lithium ion battery anode material having high energy density, and manufacturing method thereof.
Description of Related Art
Lithium-ion battery has prominent advantages such as high energy density, long cycle life, low self-discharge rate, no memory effect, good security, etc., which results that there is a wide range of applications in the production and life, such as portable electronics, power supply, energy storage power plants and other areas. With the demand for improvement of living standards and technological progress, the development of lithium-ion batteries also made many new requirements, and there is urgent need to develop a higher energy density, better safety battery.
To improve and enhance the performance of the anode material, which is one of the core parts of lithium-ion battery, is one of the key point to enhance the performance of lithium-ion batteries, and also the focus of research and development.
The use of Nickel, cobalt and manganese ternary layered material gradually increases in practical applications since it has more prominent advantages. Among that, high-nickel ternary layered material, because of its high capacity, good rate performance, low price, is considered as the most promising used anode material in digital products, hybrid electric vehicles, plug-in electric vehicles, pure electric vehicles and other power batteries.
High nickel material has the shortcomings such as high surface activity, readily reduced for nickel, etc., so the present-used improved method is to coat the material surface with a layer of inert material, such as Al2O3, MgO, SiO2, AlF3, Ni3 (PO4)2, AlPO4, etc. Currently, most of the coating process is carried out to the sintered material. For example, first, preparing the Ni, Co, Mn hydroxide or carbonate precursor, and sintering after mixed with the lithium salt, thereby obtaining the nickel-cobalt-manganese ternary layered material, then continue to subsidencing or adsorbing hydroxides, carbonates corresponding to the coating material to the surface. Hydroxides or carbonates decompose at high temperatures into the corresponding coating material by calcining again, thus getting the coated anode material.
The principle of coating is to reduce the direct contact of high nickel material to the air and electrolytic solution. H2O is the most harmful to the electrode material in the electrolytic solution, which can react with the electrolyte to generate HF etching electrode dissolution of transition metals in the anode material. After coating with the oxide, the trace HF in the electrolyte would react with the oxide to result corresponding fluoride deposited on the surface and continue to play a protective role of the anode material. Although this process is capable of forming a cladding layer, but due to the coating process typically requires a treatment in which sintered high nickel material should be placed in water or an organic solvent, which requires an additional secondary calcination. Moreover, Ni3+ in some lattices will inevitably be reduced to NiO during calcination, which results in the forming of spinel phase in local, and causing the material to reduce capacity, cycle degradation, gas producing, and increase of the battery safety hazard. In addition, the coating content of the current coating method and process is of comparatively small amount, thus unable to form a uniform coating layer. Also, the cladding layer is not electrochemically active material and do not possess deintercalation capacity for the lithium ions.
Consequently, there is an urgent need to provide a method for preparing a new anode material so as to make the nickel element in the core part difficult to spread to the surface and being reduced.